I think it's important when considering lists like the ones you've linked to examine the dates these structures were built. For its time, the Hoover Dam was the largest in the world, but isn't simply the dam itself that represents an impressive feat of engineering. The work that went into diverting the Colorado River was (and still is) probably one of the most remarkable efforts undertaken, with the likely exception of the Three Gorges Dam. Either way, it's important to remember that this was a structure started in the 1930s. The age, materials available, the material science known at that time, and so forth are the reasons structures remain important samples of architectural engineering long after they've been eclipsed by more modern developments. Hence why it's difficult to tell if you're genuinely curious or simply levying unwarranted criticism against categorizing the Hoover Dam as a "marvel."
In other words, it's in our nature, for whatever reason, to continue building structures that grow ever larger, require greater understanding of materials--better materials, too--and shadow efforts of the past with new, more impressive, modern designs. However, that doesn't supplant those past efforts simply because they've been outdone. Otherwise, we wouldn't still consider the Great Wall of China one of the world's wonders (which in spite of our present technology still remains an incredible structure mostly unsurpassed by modern efforts).
You could also examine other answers to this same question if you don't find my response convincing [1].
I think it's important when considering lists like the ones you've linked to examine the dates these structures were built. For its time, the Hoover Dam was the largest in the world, but isn't simply the dam itself that represents an impressive feat of engineering. The work that went into diverting the Colorado River was (and still is) probably one of the most remarkable efforts undertaken, with the likely exception of the Three Gorges Dam. Either way, it's important to remember that this was a structure started in the 1930s. The age, materials available, the material science known at that time, and so forth are the reasons structures remain important samples of architectural engineering long after they've been eclipsed by more modern developments. Hence why it's difficult to tell if you're genuinely curious or simply levying unwarranted criticism against categorizing the Hoover Dam as a "marvel."
In other words, it's in our nature, for whatever reason, to continue building structures that grow ever larger, require greater understanding of materials--better materials, too--and shadow efforts of the past with new, more impressive, modern designs. However, that doesn't supplant those past efforts simply because they've been outdone. Otherwise, we wouldn't still consider the Great Wall of China one of the world's wonders (which in spite of our present technology still remains an incredible structure mostly unsurpassed by modern efforts).
You could also examine other answers to this same question if you don't find my response convincing [1].
[1] https://www.google.com/search?q=why+is+hoove+dam+an+engineer...